Journal article

Publication year: 2012

Pages: 13641-13650

Journal: Journal of the American Chemical Society

Volume number: 134

Issue number: 33

ISSN: 0002-7863

DOI Link: https://doi.org/10.1021/ja302258q

Publisher: American Chemical Society

Abstract: 

The metal-induced coupling of tertiary diamondoid bromides gave highly
sterically congested hydrocarbon (hetero)dimers with exceptionally long
central C–C bonds of up to 1.71 Å in 2-(1-diamantyl)[121]tetramantane.
Yet, these dimers are thermally very stable even at temperatures above
200 °C, which is not in line with common C–C bond length versus bond
strengths correlations. We suggest that the extraordinary stabilization
arises from numerous intramolecular van der Waals attractions between
the neighboring H-terminated diamond-like surfaces. The C–C bond
rotational dynamics of 1-(1-adamantyl)diamantane,
1-(1-diamantyl)diamantane, 2-(1-adamantyl)triamantane,
2-(1-diamantyl)triamantane, and 2-(1-diamantyl)[121]tetramantane were
studied through variable-temperature ¹H- and ¹³C NMR spectroscopies. The shapes of the inward (endo) CH surfaces determine the dynamic behavior, changing the central C–C bond rotation barriers from 7 to 33 kcal mol^–1. We probe the ability of popular density functional theory (DFT) approaches (including BLYP, B3LYP, B98, B3LYP-Dn,
B97D, B3PW91, BHandHLYP, B3P86, PBE1PBE, wB97XD, and M06-2X) with
6-31G(d,p) and cc-pVDZ basis sets to describe such an unusual bonding
situation. Only functionals accounting for dispersion are able to
reproduce the experimental geometries, while most DFT functionals are
able to reproduce the experimental rotational barriers due to error
cancellations. Computations on larger diamondoids reveal that the
interplay between the shapes and the sizes of the CH surfaces may even
allow the preparation of open-shell alkyl radical dimers (and possibly
polymers) that are strongly held together exclusively by dispersion
forces.

Harvard Citation style: Fokin, A., Chernish, L., Gunchenko, P., Tikhonchuk, E., Hausmann, H., Serafin, M., et al. (2012) Stable Alkanes Containing Very Long Carbon–Carbon Bonds, Journal of the American Chemical Society, 134(33), pp. 13641-13650. https://doi.org/10.1021/ja302258q

APA Citation style: Fokin, A., Chernish, L., Gunchenko, P., Tikhonchuk, E., Hausmann, H., Serafin, M., Dahl, J., Carlson, R., & Schreiner, P. (2012). Stable Alkanes Containing Very Long Carbon–Carbon Bonds. Journal of the American Chemical Society. 134(33), 13641-13650. https://doi.org/10.1021/ja302258q